Drafting instrument

ABSTRACT

A drafting instrument comprising relatively adjustable divergent arms and a resiliently flexible spring tape having spirally curved end portions selectively engaged by the arms. A curvature control lever is engageable selectively with the spring tape to control in cooperation with the arms the curvilinear shape of the spring tape for tracing the selected curvilinear shape thus effected.

United States Patent Arrieta Apr. 22, 1975 DRAFTING INSTRUMENT 2.813.71011/1957 Angle 7. 33/177 [76] Inventor: Daniel Aguilar Arrieta. P.O.FOREIGN PATENTS 0 PPL Ns (Apartado) 1929 San Jose Costa 435.857 5/1948Italy 33/177 R1ca [22] Filed: July 17, 1973 Primary E.\'an1inerRichardE. Aegerter Assistant E.\'an1iner--.lohn W. Shepperd 21 A LN 379,996 1pp D Attorney, Agent, or FirmH1ll, Gross, S1mpson, San

Santen, Steadman. Chiara & Simpson [52] US. Cl 33/177; 269/45 [51] Int.Cl. B43] 13/20 [58] Field of Search 33/179, 177, l76; 269/45, [571ABSTRACT 269/275 A drafting instrument comprising relatively adjustabledivergent arms and a resiliently flexible spring tape [56] ReferencesCited having spirally curved end portions selectively en- UNITED STATESTS gaged by the arms. A curvature control lever is en- 853 426 5/1907Stccnstrup 769/45 gageable selectively with the spring tape to controlin 1 157345 10/1915 T0111.........1:2:111:11:I: 33 177 (Operation withthe arms the curvilinear Shape 0f the l:689:234 10/1928 Filzcr Spring pfor tracing the Selected curvilinear Shape 1138,494 l 1/1938 Knox thuseffected.

2.217.998 lO/l940 Buttress 2.519.107 8 1950 Brown 269/275 5 Claims, 8Drawmg Flgllres DRAFTING INSTRUMENT such an instrument for providing aninfinite range of curves to assist in various pattern and draftingsituations.

Regular curves are fairly easily found and are provided by various fixedinstruments such as the well known French curves. However, numeroussituations require curvilinear variations that are either rather complexor at least are not readily found in a fixed pattern or instrument.

It is an important object of the present invention to provide a new andimproved drafting instrument by which numerous and varied curves can beeffected easily and quickly.

Another object of the invention is to provide a new and improveddrafting instrument having a resiliently flexible strip material such asclock spring material.

A further object of the invention is to provide a new and improveddrafting instrument having novel means for controlling the curvature ofa flexibly resilient strip or band of material.

Other objects, features and advantages of the invention will be readilyapparent from the following description of a preferred embodimentthereof. taken in conjunction with the'accompanying drawing althoughvariations and modifications may be effected without departing from thespirit and scope of the novel concepts embodied in the disclosure, andin which:

FIG. 1' is a top plan ofa drafting instrument embodying features of theinvention.

FIG. 2 is a detail view showing certain features of the spring tape ofthe invention.

FIG. 2A is an elevational view showing a portion of the tape.

FIG. 2B is a prospective view of the center member.

FIG. 3 is an elevational view of the instrument.

FIG. 4 is a perspective view of a spacer member used in the instrument.

FIG. 5 is an exploded elevational view of the curvature control lever ofthe instrument.

FIG. 6 is an isometric view of a coupling used with the control lever.

The present invention is adapted to be employed in various draftingsituations, such as, architectonic drawing, architecture, orography,mathematics, geology, artistic drawing. statistics, engineeringmeterology, shoemaking, carpentry, tailoring, commercial drawing,precission mechanics, electronics, mining. There are other uses in whicha variable pattern drafting instrument is valuable such as: in anatomyin order to draw the muscles or build a model in clay or paste for themedicine studies in which is necessary to distinguish a muscle from theother, under the different shapes acquired by the pattern. Inengineering is the broadest field, because in all of the branches it canbe used very frequently because the student helps himself to build themathematical curves which are necessary to study the different phenomenapresented in the said study.

The main principle of the present apparatus is to maintain to differentshapes a spiral spring or a deflected band which normally tends toremain in straight line. In this case, there are two spirals joined as asingle tape or band, with the spiral centers staying at a certaindistance due to arms formed from plates, one above and one below, whichby means of clamps secure the band very tight. The plates connected thisway, cooperate to hold the tape rigidly in the desired form in which isis to be employed. The mechanism which will be discussed later allowsthe operator to release the tape totally or partially and then work withit. In mechanical engineering there is a very appropriate work concernedwith oscillatory movements with softening in which is necessary a curvepattern that gives eliptic forms in order to present it graphically, andthis is used for the design of some machines. In orogaphy, geology orany other science it is used to draw elevation curves. In tailoring itis employed in the designing of clothes, giving greater flexibility tosuch designing. The arms of the device may be as simple as two platesjoined by a screw which can be clamped to a spiral tape and thataccomplishes the requirements mentioned above.

A sample of variable plate is like the one presented in FIG. 1. The tapeof double spiral is represented with the letter A. The locations ofrectangular holes 0 (FIG. 2) made in the longitudinal centerline of thetape, looking from the front, are represented al to a7, respectively.The arm system is represented in its entirety by B. A control leverconnects the holes of the tape with the arms and is identified by C2.The circle Cl can also receive the mounting for the lever C2 or anotherof the said levers which allows greater complexity of the curves thatare desired to project. The arm system B is two pairs of platescomprising a pair of upper and lower plates, upper plate B1 and lowerplate Bl and a pair of plates comprising an upper plate B2 and a lowerplate B2 joined in divergent relation at one end by means of a screw Tby which different angles. as well as flexible adjustments for differentpositions can be attained. With the screw T the arms can be variablyadjusted relatively to provide an infinity of various forms of curve andgreater or smaller radius of curvatures.

The indicated points P1, P2, P3, and P4 are the different strategicpositions in which one can put the pin 10 that represents approximatelythe center of any of the two ellipsi. according to the desire of theoperator. This way one can achieve making greater or smaller any of theinternal curves of the ellipsi moved to P2 or P3. Isolating each one ofthe parts of the pattern one can attain a variable curvature pattern. Itwill be seen that one half of the spiral shape tape A, which is made ofmetal with a width h exerts a force of expansion in the same way as aclock spring, is at its internal extremity rigidly joined to the pin 10with a groove 11 that comes out to the end at the upper plate in orderto be able, as desired to move the tape to contract it or expand it. Theholes al, a2, and a3, are represented in FIG. 2. In those holes willenter the head N3 of the lever C2, or Cl if it also exists, and the oneleft will enter in another hole. Viewing the arm plate system in FIG. 3,one can see the fastener clamps S1 and S2, arrows indicating thedirection in which the plates are pressed against the tape. Layers ofresistent rubber HI and H2 are provided to give immobility to the tape,allowing it a better handling to the operator. The screw T with a handor wingnut secures the four plates B1 and B2 simultaneously, leavingthem immovable, due to the fact that there is a cylindrical spacer Jwhich allows the said operation.

Referring to the levers C1 or C2, (FIG. 5) the two of them are equal.The screw M could be soldered to the plate B1 or B2. The screw andwasher parts K, L are only used to fasten the lever bar C2. The head Uof the bar C2 is slotted, as shown, and receives a neck N2 of a couplingN which has a retaining tail N1 at one end and a head N3 at the oppositeend and which coincides in size with any of the holes a1. a2, etc. ofthe tape, and has a rotating movement, to facilitate coupling to thetape A for maintaining any desired curvature.

In use of the instrument the lower plates B1 and B2 offer an advantageto the operator, in that they maintain the tape A to a certain heightover a surface on which a pencil or pen traces the curvature of the bandA. The plates should be easily slidable over the flat surface of thetable over which one is going to draw or make sketches. Supposing thatwhat is being designed is a cam for a certain engine and one has thepoints over which a curve will be designed to coincide with them all.the device of the present invention is adjusted to dispose the tape A tothe best curvature between the mentioned points trying as nearly aspossible to obtain more than 50 percent of the profile of the cam,assuring perfection of the curve for the rest of the curve to follow.The levers Cl and C2 are useful in more elaborate efforts in which thecurves change directions or allow a new sketch in a given position. Ifone would like to know the concavity of a surface in a hole in which thedevice may fit easily, one can take advantage of the characteristicsof'the spring and tighten the fasteners 51 and S2 in order to maintainthe said curvature.

It will be understood that variations and modifications may be effectedwithout departing from the spirit and scope of the novel concepts ofthis invention.

I claim as my invention:

1. A drafting instrument for selectively producing a large variety oftraceable curves, comprising:

a resiliently flexible spring band having opposite expansile spiral endportions and each end portion having a terminal within the spiralthereof;

two pairs of elongated top and bottom clamping plates which generallycoextensive in each pair and each pair providing a respective arm;

means connecting proximal end portions of the pairs of plates togetherwith the plates of each pair spaced apart, and said connecting meansincluding fastening structure operable for adjustably securing the armsin various divergent relative positions;

means connecting the terminal of one of said spiral end portions betweenthe distal end portion of one of said pair of plates, and meansconnecting the terminal of the other of said spiral end portions betweenthe distal end portions of the other of said pairs of plates;

at least one elongated control lever extending between one of said armsand said band intermediate said spiral portions to maintain the band ina controlled curvature;

means adjustably connecting one end portion of the control meansadjustably attaching the control lever at its opposite end portiondirectly to one of the plates of said one arm; and means for releasablyclamping said spiral protions of said band between said plates wherebyto hold the band in predetermined adjusted curvatures.

2. An instrument according to claim 1, wherein said band has a series oflongitudinally spaced apertures therein, and said means connecting saidone end of said lever to the band being selectively engageable in anyone of said apertures in the band.

3. An instrument according to claim 1, wherein said band has a series oflongitudinally spaced apertures therein, and said means connecting saidone of the lever to the band comprising a coupling selectivelyengageable in any one of said apertures in the band.

4. An instrument according to claim 1, including resilientlycompressible surfacing material carried by at least one of the plates ofeach of said pairs of plates on the surface of said at least one platewhich faces toward the edge of the associated spiral end portion of theband, and said compressible facing means engaging said edges of theassociated spiral end portion of the band and thereby positively holdingthe spiral end portions to assist-in retaining the band in'selectedcurve adjustments.

5. An instrument according'to claim 1, wherein said pairs of platesinclude in each pair a lower plate to engage a supporting surface, saidlower plates having bottom surfaces which are coplanar so as to lie flatin the same plane on a drawing surface, one of said lower plates havingits proximal end portion offset to the thickness of the lower plate ofthe other pair of plates and lapping said lower plate of the other ofsaid plates whereby to provide for the coplanar bottom surfacerelationship.

1. A drafting instrument for selectively producing a large variety oftraceable curves, comprising: a resiliently flexible spring band havingopposite expansile spiral end portions and each end portion having aterminal within the spiral thereof; two pairs of elongated top andbottom clamping plates which generally coextensive in each pair and eachpair providing a respective arm; means connecting proximal end portionsof the pairs of plates together with the plates of each pair spacedapart, and said connecting means including fastening structure operablefor adjustably securing the arms in various divergent relativepositions; means connecting the terminal of one of said spiral endportions between the distal end portion of one of said pair of plates,and means connecting the terminal of the other of said spiral endportions between the distal end portions of the other of said pairs ofplates; at least one elongated control lever extending between one ofsaid arms and said band intermediate said spiral portions to maintainthe band in a controlled curvature; means adjustably connecting one endportion of the control means adjustably attaching the control lever atits opposite end portion directly to one of the plates of said one arm;and means for releasably clamping said spiral protions of said bandbetween said plates whereby to hold the band in predetermined adjustedcurvatures.
 1. A drafting instrument for selectively producing a largevariety of traceable curves, comprising: a resiliently flexible springband having opposite expansile spiral end portions and each end portionhaving a terminal within the spiral thereof; two pairs of elongated topand bottom clamping plates which generally coextensive in each pair andeach pair providing a respective arm; means connecting proximal endportions of the pairs of plates together with the plates of each pairspaced apart, and said connecting means including fastening structureoperable for adjustably securing the arms in various divergent relativepositions; means connecting the terminal of one of said spiral endportions between the distal end portion of one of said pair of plates,and means connecting the terminal of the other of said spiral endportions between the distal end portions of the other of said pairs ofplates; at least one elongated control lever extending between one ofsaid arms and said band intermediate said spiral portions to maintainthe band in a controlled curvature; means adjustably connecting one endportion of the control means adjustably attaching the control lever atits opposite end portion directly to one of the plates of said one arm;and means for releasably clamping said spiral protions of said bandbetween said plates whereby to hold the band in predetermined adjustedcurvatures.
 2. An instrument according to claim 1, wherein said band hasa series of longitudinally spaced apertures therein, and said meansconnecting said one end of said lever to the band being selectivelyengageable in any one of said apertures in the band.
 3. An instrumentaccording to claim 1, wherein said band has a series of longitudinallyspaced apertures therein, and said means connecting said one of thelever to the band comprising a coupling selectively engageable in anyone of said apertures in the band.
 4. An instrument according to claim1, including resiliently compressible surfacing material carried by atleast one of the plates of each of said pairs of plates on the surfaceof said at least one plate which faces toward the edge of the associatedspiral end portion of the band, and said compressible facing meansengaging said edges Of the associated spiral end portion of the band andthereby positively holding the spiral end portions to assist inretaining the band in selected curve adjustments.